This project is aimed at developing noise reduction algorithms for improving the intelligibility of speech for cochlear implant users. Phase 1 work showed that using directional microphone arrays in conjunction with dual-channel noise reduction algorithms improves speech reception in noise for cochlear implant users. The proposed Phase 2 work will expand the scope to include noise reduction techniques at every possible point in the cochlear implant acoustic pick-up and signal processing chain. The work considers single and dual microphone arrays, single- or dual-channel preprocessing algorithms, and novel within-channel compressor- control algorithms. Each of these approaches will be studied using methods that range from computer simulations and automatic intelligibility prediction, for rapid system assessments, to speech-reception testing and listening-quality ratings by cochlear implant users with portable real-time signal processing for formal evaluations. Acoustic test environments (simulated or actual) will be realistic with respect to the degree of reverberation, and the number and stationarity of interference sources. A final comprehensive study will evaluate the contributions of optimized signal-processing algorithms in conjunction with four different microphone-array configurations. The results of this work will quantify the benefits of optimized noise reduction options for cochlear implant users. The most promising algorithms will be developed in Phase 3 work through contractual agreements with commercial partners. Cochlear implants are the only viable procedure for restoring a sense of hearing to profoundly deafened individuals. Progress in cochlear implants has increased to the point where many recipients can understand speech in quiet without the aid of lip-reading; however, susceptibility to background noise continues to be much worse for recipients than for normal hearing listeners. The goal of this project is to develop noise reduction systems to improve speech reception for cochlear implant users in the presence of background noise. [unreadable] [unreadable] [unreadable]